The present invention is related to a moveable portion of a fluid control valve that may be actively positioned, anywhere between an extreme open condition and an extreme closed condition, to adjust a flow of fluid passing therethrough. The invention is particularly useful in valves intended for proportional or modulating control of fluid delivery within industrial processes making semiconductor devices, pharmaceuticals, or fine chemicals, and many similar high-purity fluid delivery systems that simultaneously demand a leak-tight shut-off in the fully closed condition along with proportional control. Many combinations of metallic and elastomeric elements enhancing valve shut-off are known in the art.